I always remove it as sometimes we had the barrels returned without the bush. They tend to forget about it and once in the acid bath its gone...

You need to find a shaft that will fit into the bush tightly, eg. an old drill bit, or new one...

Then you apply grease to "pack" the bush, then tap the shaft with a hammer to hydraulically lift the bush out of the barrel. (The shaft forces the grease underneath the bush to push it out.)

You might have to pack the bush more than once with grease.

Cheers
Mario